Diane E. Pataki

Context: Urban and nearby non-urban landscapes differ in vegetation and surface climate. How these differences vary with hydroclimate over multiple decades remains poorly resolved. Objectives: We compared urban and reference greenness and land surface temperature across U.S. climates. We also evaluated differences in trajectories, spatial variability, and precipitation dependence. Methods: We analyzed harmonized Landsat observations for 52 U.S. city–reference pairs over 1995–2024. Comparisons used fixed footprints, environmental covariates, and supplementary sensitivity analyses. Results: Across 52 pairs, the median city was less green (ΔNDVI = − 0.17) and warmer (ΔLST = + 5.09 °C) than its reference. These differences reversed along the climatic gradient, with arid cities often greener and cooler and mesic cities generally less green and warmer than their references. In paired annual composites, cities warmed approximately 22% faster than references on average, while urban NDVI changed little or declined slightly and references greened. Greenness was more spatially variable in every urban footprint by CV and SD, and this difference persisted in 36 qualifying equal-area comparisons. Precipitation responses were strongest in dry settings and generally weaker in cities. Conclusions: Urban–reference differences varied predictably with regional hydroclimate, while cities and references followed diverging long-term trajectories. Greater urban greenness heterogeneity persisted after accounting for sampling area and shape. These observations support an inter-urban water-deficit framework that considers regional hydroclimate and urban land cover when comparing landscapes and their trajectories.

The magnitude and fate of irrigation water are important variables in both urban hydrology and sustainability science. Studies of urban irrigation are relatively few compared to agricultural irrigation. Yet, a growing number of ecohydrologic measurements in cities are revealing general trends in drivers of irrigation practices and their impacts on urban water budgets. Urban irrigation rates are strongly influenced by social factors and highly variable due to intra‐ and inter‐urban land use heterogeneity, climate conditions, water pricing, landscaping norms and behaviors, and water management policies. Irrigation is lost from landscapes through evapotranspiration (ET), surface runoff, or groundwater recharge. Of these fluxes, ET has been the most well‐studied. ET is more strongly driven by climatic variables than irrigation rates, particularly vapor pressure deficit for rough, open canopies and incoming radiation for smooth canopies such as turfgrass lawns, which tend to have much higher ET rates than urban trees. Recent measurements have shown a saturating relationship between ET and irrigation, with many land owners irrigating their yards well in excess of maximum rates of ET. Although urban landscapes can mitigate stormwater runoff, excess irrigation contributes to urban runoff and groundwater, which may exacerbate water quality problems when contaminated with fertilizers or pesticides. Overall, many opportunities still exist to improve the efficiency of urban irrigation while maintaining ecosystem services of irrigated landscapes. By filling critical data and mechanistic gaps, socioecohydrologic studies of irrigated cities can greatly support urban water sustainability.

Despite interest in the contribution of evapotranspiration (ET) of residential turfgrass lawns to household and municipal water budgets across the United States, the spatial and temporal variability of residential lawn ET across large scales is highly uncertain. We measured instantaneous ET (ET_inst) of lawns in 79 residential yards in six metropolitan areas: Baltimore, Boston, Miami, Minneapolis‐St. Paul (mesic climates), Los Angeles and Phoenix (arid climates). Each yard had one of four landscape types and management practices: traditional lawn‐dominated yards with high or low fertilizer input, yards with water‐conserving features, and yards with wildlife‐friendly features. We measured ET_inst in situ during the growing season using portable chambers and identified environmental and anthropogenic factors controlling ET in residential lawns. For each household, we used ET_inst to estimate daily ET of the lawn (ET_daily) and multiplied ET_daily by the lawn area to estimate the total volume of water lost through ET of the lawn (ET_vol). ET_daily varied from 0.9 ± 0.4 mm d¹ in mesic cities to 2.9 ± 0.7 mm d⁻¹ in arid cities. Neither ET_inst nor ET_daily was significantly influenced by yard landscape types and ET_inst patterns indicated that lawns may be largely decoupled from regional rain‐driven climate patterns. ET_vol ranged from ∼0 L d⁻¹ to over 2,000 L d⁻¹, proportionally increasing with lawn area. Current irrigation and lawn management practices did not necessarily result in different ET_inst or ET_daily among traditional, water‐conserving, or wildlife‐friendly yards, but smaller lawn areas in water‐conserving and wildlife‐friendly yards resulted in lower ET_vol.

Urban regions emit a large fraction of anthropogenic emissions of greenhouse gases (GHG) such as carbon dioxide (CO₂) and methane (CH₄) that contribute to modern-day climate change. As such, a growing number of urban policymakers and stakeholders are adopting emission reduction targets and implementing policies to reach those targets. Over the past two decades research teams have established urban GHG monitoring networks to determine how much, where, and why a particular city emits GHGs, and to track changes in emissions over time. Coordination among these efforts has been limited, restricting the scope of analyses and insights. Here we present a harmonized data set synthesizing urban GHG observations from cities with monitoring networks across North America that will facilitate cross-city analyses and address scientific questions that are difficult to address in isolation.

Societal Impact Statement: Globally, cities are planning for resilience through urban greening initiatives as governments understand the importance of urban forests in improving quality of life and mitigating climate change. However, the persistence of urban forests and the ecosystem benefits they provide are threatened by climate change, and systematic assessments of causes of tree dieback and mortality in urban environments are rare. Long‐term monitoring studies and adaptive management are needed to identify and prevent climate change‐driven failures and mortality. Research and monitoring when coupled with systematic forecasting will enable governments to incorporate climate change resilience into urban forestry planning. Future scenarios in which urban forests are resilient or in decline will depend on the management and planning actions we make today.Summary: The management of urban forests is a key element of resilience planning in cities across the globe. Urban forests provide ecosystem services as well as other nature‐based solutions to 4.2 billion people living in cities. However, to continue to do so effectively, urban forests need to be able to thrive in an increasingly changing climate. Trees in cities are vulnerable to extreme heat and drought events, which are predicted to increase in frequency and severity under climate change. Knowledge of species' vulnerability to climate change, therefore, is crucial to ensure provision of desired ecosystem benefits, improve species selection, maintain tree growth and reduce tree mortality, dieback and stress in urban forests. Yet, systematic assessments of causes of tree dieback and mortality in urban environments are rare. We reviewed the state of knowledge of tree mortality in urban forests globally, finding very few frameworks that enable detection of climate change impacts on urban forests and no long‐term studies assessing climate change as a direct driver of urban tree dieback and mortality. The effects of climate change on urban forests remain poorly understood and quantified, constraining the ability of governments to incorporate climate change resilience into urban forestry planning.

In cities, humans directly and indirectly affect plant and wildlife communities. These human–species interactions are not included in traditional ecological approaches used to understand why and how organisms are distributed. Here, we incorporate human behaviors into urban community assembly theories and detail all the complex ways humans affect the dispersal, selection and persistence of species in cities. To do this, we integrate human behaviors and actions into traditional filter frameworks used to study community assembly. We use our framework to develop testable hypotheses to predict patterns of urban diversity as well as pose key considerations for future research. In order to have a predictive understanding of how urban biodiversity responds to environmental, social and land use change, it is necessary to better understand interactions between humans and other organisms.

The 2085 km²Jordan River Basin, and its seven sub‐catchments draining the Central Wasatch Range immediately east of Salt Lake City, UT, are home to an array of hydrologic, atmospheric, climatic and chemical research infrastructure that collectively forms the Wasatch Environmental Observatory (WEO). WEO is geographically nested within a wildland to urban land‐use gradient and built upon a strong foundation of over a century of discharge and climate records. A 2200 m gradient in elevation results in variable precipitation, temperature and vegetation patterns. Soil and subsurface structure reflect systematic variation in geology from granitic, intrusive to mixed sedimentary clastic across headwater catchments, all draining to the alluvial or colluvial sediments of the former Lake Bonneville. Winter snowfall and spring snowmelt control annual hydroclimate, rapid population growth dominates geographic change in lower elevations and urban gas and particle emissions contribute to episodes of severe air pollution in this closed‐basin. Long‐term hydroclimate observations across this diverse landscape provide the foundation for an expanding network of infrastructure in both montane and urban landscapes. Current infrastructure supports both basic and applied research in atmospheric chemistry, biogeochemistry, climate, ecology, hydrology, meteorology, resource management and urban redesign that is augmented through strong partnerships with cooperating agencies. These features allow WEO to serve as a unique natural laboratory for addressing research questions facing seasonally snow‐covered, semi‐arid regions in a rapidly changing world and an excellent facility for providing student education and research training.

Societal Impact Statement: It is increasingly common for plant scientists and urban planning and design professionals to collaborate on interdisciplinary teams that integrate scientific experiments into public and social urban spaces. However, neither the procedural ethics that govern scientific experimentation, nor the professional ethics of urban design and planning practice, fully account for the possible impacts of urban ecological experiments on local residents and communities. Scientists that participate in design and planning teams act as decision‐makers, and must expand their domain of ethical consideration accordingly. Conversely, practitioners who engage in ecological experiments take on the moral responsibilities inherent in generation of knowledge. To avoid potential harm to human and non‐human inhabitants of cities while maintaining scientific and professional integrity in research and practice, an integrated ethical framework is needed for urban ecological planning and design.Summary: While there are many ethical and procedural guidelines for scientists who wish to inform decision‐making and public policy, urban ecologists are increasingly embedded in planning and design teams to integrate scientific measurements and experiments into urban landscapes. These scientists are not just informing decision‐making – they are themselves acting as decision‐makers. As such, researchers take on additional moral obligations beyond scientific procedural ethics when designing and conducting ecological design and planning experiments. We describe the growing field of urban ecological design and planning and present a framework for expanding the ethical considerations of socioecological researchers and urban practitioners who collaborate on interdisciplinary teams. Drawing on existing ethical frameworks from a range of disciplines, we outline possible ways in which ecologists, social scientists, and practitioners should expand the traditional ethical considerations of their work to ensure that urban residents, communities, and non‐human entities are not harmed as researchers and practitioners carry out their individual obligations to clients, municipalities, and scientific practice. We present an integrated framework to aid in the development of ethical codes for research, practice, and education in integrated urban ecology, socioenvironmental sciences, and design and planning.